The PK_a of the α−Carboxyl Group of an Amino Acid

Question

The pKaof the α−carboxyl group of an amino acid is ____ by the presence on the amine group.
A) greatly increased (>2 pH units)
B) greatly decreased (> 2 pH units)
C) unchanged
D) slightly increased (1-2 pH units)
E) slightly decreased (1-2 pH units)

Accepted Answer

The presence of the amine group on an amino acid can lead to protonation of the α−carboxyl group, which would decrease the pK_a value by more than 2 pH units. This is due to the electron-withdrawing effect of the positively charged amine group, which stabilizes the negatively charged carboxylate group and makes it more acidic.

The pKa of the α−carboxyl group of an amino acid is ____ by the presence on the amine group.

The pK_a of the α−carboxyl group of an amino acid is ____ by the presence on the amine group.